This invention relates generally to doors for microwave cooking ovens and more particularly to a latch assembly for a microwave heating apparatus.
In a conventional microwave heating apparatus, such as a microwave oven, a microwave frequency of about 2450 MHz is used to cook various food products. In such microwave ovens, if the cabinet door does not completely close, microwaves leak outside of the oven through a narrow air gap around the periphery of the door. The leakage of the microwave adversely affects nearby electric devices, such as a television receiver, and is also harmful to nearby persons.
Accordingly, it is desirable not only to completely close the door during cooking operations but also to deenergize the microwave generator when the door is opened. To accomplish this function, various kinds of door latches are well known as shown, for example, in U.S. Pat. Nos. 3,715,552 and 3,777,098.
However, since the magnetron is re-energized if the door is closed and then opened within the cooking operating time, there is a danger of operating the oven without the food products therein if these food products are removed before the door is again closed.
Accordingly, the microwave oven is usually designed as shown in Japanese published Utility Model No. 54-1056 and No. 54-38307 published respectively on Jan. 19, and Nov. 14, 1979. Namely, the microwave oven has a mechanical locking assembly which operates such that the magnetron is not energized unless the cook starting button is operated when the door is in its closed position. The conventional door latch assembly is very complicated because it has springs to operate the switch assembly disposed in the generating circuit. These springs must be carefully selected to achieve the desired switching action and they deteriorate with use thus making it difficult to obtain consistent, long-term durability. It is also difficult to manufacture the door latch assembly because of the many parts thereof.